This relates generally to imaging systems and, more particularly, to imaging systems that have logarithmic pixels.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Image sensors (sometimes referred to as imagers) may be formed from a two-dimensional array of image sensing pixels. Each pixel includes a photosensitive layer that receives incident photons (light) and converts the photons into electrical charge. Image sensors are sometimes designed to provide images to electronic devices using a Joint Photographic Experts Group (JPEG) format.
Image sensors may include logarithmic pixels or linear pixels. Linear pixels may accumulate charge in a photosensitive layer over some integration time. After the integration time is complete, the accumulated charge may be transferred and sampled. The sampled voltage that is associated with the accumulated charge may be proportional to the intensity of the incident light. Alternatively, logarithmic pixels may continuously measure light intensity without accumulating charge. At any point, a voltage in the logarithmic pixel may be sampled that is proportional to the logarithm of the intensity of the incident light. Because logarithmic pixels are continuously measuring exposure to incident light, it may be difficult to remove noise from the sample. Logarithmic pixels may therefore be subject to pixel fixed pattern noise.
It would therefore be desirable to provide improved logarithmic pixels.